水溶液中稀土离子与甘氨酸、丝氨酸、天冬氨酸作用的13C NMR研究

测定了酸性水溶液中甘氨酸、丝氨酸和天冬氨酸稀土络合物(Ln=La、Pr、Nd、Eu、Tb、Dy、Ho、Er、Tm和Yb)的¹³C诱导位移。对位移试剂的分析指出,三种氨基酸通过α-羧基以双齿形式配位于稀土,配位键长为0.23nm~0.25nm,天冬氨酸的γ-羧基也是配位基团。由本文与文献中已报道的各种氨基酸稀土络合物的¹³C诱导位移的系统分析表明,配体¹³C超精细偶合常数A值和结构因子G值有如下规律:(1)│A(C₀)│<│A(C_α)│;A(C₀)为正,A(C_α)为负;(2)│G(C₀)│>│G(C_α)│;配体碳核的G均为负值。     

High-spin g factors and proton alignment in Pt

The average g factors of high-spin states in ^180,182,184Pt were measured by the transient-field technique. In all three isotopes the quasicontinuum g factor at an angular momentum of 20 is g0.37. This contrasts with similar measurements on other nuclei that have 70Z80, where typical values of g0.22 have been attributed to the influence of quasineutron alignments. Evidently proton and neutron configurations are about equally important at high spin in the Pt isotopes near mid-shell. This inference is consistent with the discrete spectroscopy, including the contention, supported by g_K−g_R values, that h_9/2 proton pairs align along with the i_13/2 neutrons at rotational frequencies of ω≈0.3 MeV in ¹⁸⁴Pt. Links between the quasicontinuum g factors and features in the discrete spectroscopy are explored by comparing and contrasting the behavior of ¹⁸⁴Pt and ¹⁶⁶Hf.     

Na1/2Bi1/2TiO3体系的电子结构与极化特性

采用自洽场离散变分X_α计算方法,研究了ABO₃型钙钛矿结构无铅压电陶瓷Na_1/2Bi_1/2TiO₃体系的电子结构,分析了A,B位元素取代对Na_1/2Bi_1/2TiO₃压电陶瓷极化性能的影响.结果表明:NBT体系压电陶瓷材料存在自发极化,B位离子位移使铁电性增强,Ba,Sr与Mn离子A,B位复合取代可降低矫顽场、提高自发极化强度,从而提高材料的铁电性能,并通过实验对此结论进行了验证.     

Correlation lengths and E8 mass spectrum of the dilute A3 lattice model

The exact perturbation approach is used to derive the elementary correlation lengths ξ_i and related mass gaps mi of the two-dimensional dilute A_L lattice model in regimes 1 and 2 for L odd from the Bethe ansatz solution. In regime 2 the A₃ model is the E₈ lattice realisation of the two-dimensional Ising model in a magnetic field at T = T_c The calculations for the A₃ model in regime 2 start from the eight thermodynamically significant string types found in previous numerical studies. These string types are seen to be consistent in the ordered high field limit. The eight masses obtained reduce with the approach to criticality to the ES masses predicted by Zamolodchikov, thus providing a further direct lattice determination of the Es mass spectrum.     

How unitarity imposes a steep small-x rise of spin structure function gLT=g1+g2 and breaking of DIS sum rules

We derive a unitarity relationship between the spin structure function g_LT(x,Q²)=g₁(x,Q²)+g₂(x,Q²), the LT interference diffractive structure function and the spin-flip coupling of the pomeron to nucleons. Our diffractive mechanism gives rise to a dramatic small-x rise

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, where δ_g is an exponent of small-x rise of the unpolarized gluon density in the proton at a moderate hard scale for light flavour contribution and large hard scale for heavy flavour contribution. It invalidates the Burkhardt–Cottingham sum rule. The found small-x rise of diffraction driven g_LT(x,Q²) is steeper than given by the Wandzura–Wilczek relation under conventional assumptions on small-x behaviour of g₁(x,Q²).     

Hydrogen depth profile measurement in a-Si1-xCx:H films by elastic recoil detection

The hydrogen content and depth profile in a-Si_1-xC_x:H films were measured by the elastic recoil detection (ERD) technique. It is shown that the hydrogen content changes from 15 to 50 at% with increasing carbon content x. For x<0.4 the hydrogen content increases mainly due to the increase of the Si-CH₃ contribution and for x > 0.4 due to C-H bonds. By combining the ERD and IR results, the proportionality between the number of Si-CH₃ bonds and the intensity of IR absorption due to the Si-CH₃ rocking mode vibration is ascertained. The proportionality constant is found to be A^roc_Si-CH3 = 5 × 10¹⁹ cm^-2.     

Measurements of the spin correlation parameters Axx and Ayy for p-p scattering at 46.9 MeV

The A_xx and A_yy spin correlation coefficients of proton-proton scattering have been measured at E_lab = 46.9 MeV and θ_c.m. = 90° with the same experimental techniques already used at Saclay from 11 to 26 MeV and at Grenoble at 37.2 MeV. For A_xx the deviation from the predictions of the energy-dependent phase-shifts analysis of Livermore is significant (≈ 3.7 standard deviations) but not as large as for the 47.5 MeV Tokyo measurement. For A_yy the agreement is very good.     

27Al NMR study in ZrNiAl

We have studied the microscopic properties of the hexagonal ZrNiAl, a model compound for a wide family of intermetallic compounds crystallizing in this type of structure, by using ²⁷Al NMR spectroscopy. We have investigated the lineshape of static and MAS NMR spectra as a function of magnetic field strength (4.7–9.4 T) and temperature (5–300 K). Our data indicate that the ²⁷Al NMR spectra result from a combined effect of quadrupole and anisotropic shift interactions. The ²⁷Al nuclei are in an environment characterized by the quadrupole coupling constant e²qQ/h of 3.3 MHz, asymmetry parameter η_Q of 0.42, isotropic shift δ_iso of 393 ppm, shift anisotropy δ_anis = δ_zz − (δ_xx + δ_yy)/2 of 150 ppm, and asymmetry factor η_S of 0.5. They are found to be temperature independent. The spin–lattice relaxation rate measured at 7.05 T is proportional to the temperature with T₁T = 135 s K. The mechanisms responsible for observed values of δ_iso, δ_anis, T₁T, and the enhanced Korringa constant are discussed.     

Generalized Einstein manifolds

A Finslerian manifold is called a generalized Einstein manifold (GEM) if the Ricci directional curvature R(u,u) is independent of the direction. Let F⁰(M, g_t) be a deformation of a compact n-dimensional Finslerian manifold preserving the volume of the unitary fibre bundle W(M). We prove that the critical points g₀ F⁰(g_t) of the integral I(g_t) on W(M) of the Finslerian scalar curvature (and certain functions of the scalar curvature) define a GEM. We give an estimate of the eigenvalues of Laplacian Δ defined on W(M) operating on the functions coming from the base when (M, g) is of minima fibration with a constant scalar curvature H admitting a conformal infinitesimal deformation (CID). We obtain λ ≥ H/(n − 1) (Δf = λf). If M is simply connected and λ = H/(n − 1), then (M, g) is Riemannian and is isometric to an n-sphere. We first calculate, in the general case, the formula of the second variationals of the integral I (g_t) for G = g₀, then for a CID we show that for certain Finslerian manifolds, I″(g₀) > 0. Applications to the gravitation and electromagnetism in general relativity are given. We prove that the spaces characterizing Einstein-Maxwell equations are GEMs.     

Entropy of planar random surfaces on the lattice

We study planar random surfaces on a hypercubic lattice in two and three dimensions by Monte Carlo techniques. Our data are consistent with the formula n₀(A;C) A^b₀A, where n₀(A;C) is the number of planar random surfaces with area A and boundary C. We find b₀ = −1.4 ± 0.2, = 5.31 ± 0.03 (for d = 2) and b₀ = −1.5 ± 0.2, = 7.13 ± 0.05 (for d = 3). The values of b₀ disagree with those obtained from the Polyakov string model.     

1-forms over the moduli space of irreducible connections defined by the spectrum of Dirac operators

Let (P) be the moduli space of irreducible connections of a G-principal bundle P over a closed Riemannian spin manifold M. Let D_A be the Dirac operator of M coupled to a connection A of P and f a smooth function on M. We consider a smooth variation A(u) of A with tangent vector ω and denote T_ω:= (D_A(u)−f) (u=0. The coefficients of the asymptotic expansion of trace (T_ω · e^-t(D_A−f)2) near t=0 define 1-forms a^(k)_f, K=0, 1, 2, … on (P). In this paper we calculate aa⁽⁰⁾_f, a⁽¹⁾_f, a⁽²⁾_f and study some of their properties. For instance using the 1-form a⁽²⁾_f for suitable functions f we obtain a foliation of codimension 5 of the space of G-instantons of S⁴.     

Final-state interactions and single-spin asymmetries in semi-inclusive deep inelastic scattering

Recent measurements from the HERMES and SMC Collaborations show a remarkably large azimuthal single-spin asymmetries A_UL and A_UT of the proton in semi-inclusive pion leptoproduction γ^*(q)p→πX. We show that final-state interactions from gluon exchange between the outgoing quark and the target spectator system lead to single-spin asymmetries in deep inelastic lepton–proton scattering at leading twist in perturbative QCD; i.e., the rescattering corrections are not power-law suppressed at large photon virtuality Q² at fixed x_bj. The existence of such single-spin asymmetries requires a phase difference between two amplitudes coupling the proton target with J^z_p=±1/2 to the same final-state, the same amplitudes which are necessary to produce a nonzero proton anomalous magnetic moment. We show that the exchange of gauge particles between the outgoing quark and the proton spectators produces a Coulomb-like complex phase which depends on the angular momentum L^z of the proton's constituents and is thus distinct for different proton spin amplitudes. The single-spin asymmetry which arises from such final-state interactions does not factorize into a product of distribution function and fragmentation function, and it is not related to the transversity distribution δq(x,Q) which correlates transversely polarized quarks with the spin of the transversely polarized target nucleon.     

Ferromagnetic resonance in Sr doped rare earth orthocobaltites, Ln1−xSrxCoO3†

FMR measurements have been carried out on several members of the Ln_1−xSrxCoO₃ (Ln = Rare earth) system. The results show that g_eff in these systems is around 1.25 independent of x as well as the rare earth ion. It is suggested that this unusual value of g_eff is due to the localized intermediate-spin Co³⁺ ions (t⁵_2g e¹_g) located at the top of the π^* band.     

Testing supersymmetry in the associated production of CP-odd and charged Higgs bosons

In the Minimal Supersymmetric Standard Model (MSSM), the masses of the charged Higgs boson (H±) and the CP-odd scalar (A) are related by MH+2=MA2+mW2. Furthermore, because the coupling of W−–A–H+ is fixed by gauge interaction, the tree level production rate of depends only on one supersymmetry parameter—the mass (MA) of A. We show that to a good approximation this conclusion also holds at the one-loop level. Consequently, this process can be used to distinguish MSSM from its alternatives (such as a general two-Higgs-doublet model) by verifying the above mass relation, and to test the prediction of the MSSM on the product of the decay branching ratios of A and H± in terms of only one single parameter—MA.     

无限展长后掠翼边界层定常横流不稳定转捩分析

采用γ-Re_θt横流转捩拓展模型对NLF （2）-0415无限展长后掠机翼进行数值模拟,重点分析来流雷诺数、机翼表面粗糙度及后掠角对边界层横流不稳定性的影响.研究发现γ-Re_θt横流转捩拓展模型能够准确预测边界层定常横流不稳定转捩,计算结果与试验数据吻合较好.结果表明来流雷诺数越大、机翼表面越粗糙,横流转捩位置越靠前;随着机翼后掠角的增加,转捩位置先前移随后逐渐靠后.     

应用分子子图指数估计与预测烷烃核磁共振碳谱位移和

系统地研究了核磁共振碳谱(¹³C NMR)与化学位移规律及其定量构谱关系(QSSR).本文研究了一组多元素分子子图指数矢量(VMSG),并发现它与烷烃化学位移和(CCSA)有很好线性相关性.采用多元线性回归(MVLR)进行准确估计与预测,结果良好.     

非金属二元氢化物分子振动固有频率与pKa常数的定量关系

提出了非金属二元氢化物分子振动固有频率的计算原理与方法.将基频和总频作为结构信息指数用于非金属二元氢化物的分子结构与pK_a常数的定量关系研究,结果表明,其相关系数大于0.995,得到的回归方程用于pK_a的计算,计算值与实验值比较,平均绝对误差小于1.82.     

应用分子子图指数估计与预测烷烃核磁共振碳谱位移和

系统地研究了核磁共振碳谱(¹³C NMR)与化学位移规律及其定量构谱关系(QSSR).本文研究了一组多元素分子子图指数矢量(VMSG),并发现它与烷烃化学位移和(CCSA)有很好线性相关性.采用多元线性回归(MVLR)进行准确估计与预测,结果良好.     

Normal-state resistivity of superconducting Bi1.95Sr1.65La0.4CuO6+δ single crystals

The anisotropy of the normal-state resistivity of a number of superconducting Bi_1.95Sr_1.65La_0.4CuO_6+δ single crystals has been measured by using both a six- and a four-terminal technique. We find that the ab-plane resistivity _ab in general increases almost linearly with temperature (d_ab/dT> 0). the temperature variation of the c-axis resistivity _c, however, is strongly sample dependent. Both metallic-like (d_c/dT> 0) and mixed temperature dependences of _c, including d_c/dT < 0 are observed. The mixed _c(T) data can be well described by fitting to _c(T) = A + BT + C/T, indicating that the temperature dependence of _c(T) is the result of a competition between metallic and non-metallic terms. The temperature T_min at which _c reaches a minimum increases with increasing d_ab/dT, suggesting that the metallic term of _c arises from misaligned Cu---O planes. This is confirmed by an electron-microscope (HRTEM) analysis of the samples. The anisotropy ratio _c/_ab is of the order of 10³ but increases monotonically with decreasing temperature, indicating differences in the scattering processes parallel and perpendicular to the Cu---O plane.